In the dictionary
twinkle (intransitive): if someone’s eyes twinkle, they have a happy expression
twinkle with
Her eyes twinkled with amusement.
light up: if someone’s face or eyes light up, they show pleasure, excitement etc
with
His eyes lit up with laughter.
Her face lit up with pleasure.
My question is
What are the differences between "Her eyes twinkled" and "Her eyes lit up"?
For example, "Her eyes twinkled with pleasure / amusement" & "Her eyes lit up with pleasure / amusement"
Both expressions are metaphors that are unrelated to actual light.
Eyes "lighting up" indicates a change in expression to something happy/positive, or suddenly showing an interest in something.
Having a "twinkle in your eye" is an idiom usually meaning your expression shows happiness or amusement, or sometimes that you are keeping a secret.
twinkle implies a movement of something that has more and then less light.
For example, stars are said to twinkle because they go brighter and then less bright when gazed at by a person. It is like sparkling.
Christmas tree lights can also be said to twinkle. Some of them can go bright and then less bright. It comes from High German meaning to blink.
Whereas: to light up just means that light comes into something. If applied to eyes, it does mean pleasure or that the person is suddenly happy.
So, your eyes can light up but not necessarily twinkle. The image of eyes twinkling is like (repeat is like) the idea of there being more and then less light in your eyes. It is a metaphor.
So, light up means light comes into something. Twinkle means the light is brighter and then less bright continuously.
[Since the dictionary definitions are in the questions, they are not repeated here.]
